body{
    background-image: linear-gradient(to right, #a8edea, #a6c1ee);
}



.main{
    width: 600px;
    height: 300px;
    position: absolute;
    left: 50%;
    top: 50%;
    margin: -150px 0 0 -300px;
    padding: 100px;
    /*background-color: white;*/
    background: rgba(255,255,255,0.8);
    border-radius:10px ;
    /* x 偏移量 | y 偏移量 | 阴影模糊半径 | 阴影颜色 */
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}